New managers may sometimes have trouble assimilating to their positions. These represent some of the common mistakes managers should avoid.

1. Thinking s/he knows everything; not asking for input from other employees.
2. Focusing on showing everyone who’s in charge rather than on making a positive difference.
3. Changing everything.
4. Being too afraid to change anything.
5. Not taking the time to really know the people who work for him or her.
6. Ignoring the manager’s boss.
7. Avoiding problem employees or situations.
8. Not allowing him or herself to be human enough to laugh or make mistakes.
9. Not protecting the employees from blame, getting all the bad assignments, lower pay, etc.
10. Avoiding responsibilities; blaming failures on the group rather than him or herself.

Source: http://management.about.com